The invention concerns a snowblower comprising a blower wheel whose rotational axis runs horizontally in the snow-clearing direction; a precutting device which rotates about the same rotational axis, positioned before the blower wheel in the snow-clearing direction; and snow-clearing worm gears which rotate about vertical axes, positioned on both sides in front of the blower wheel.
Such a snowblower is disclosed in German Pat. No. 2,721,411, making it possible to feed the laterally disposed snow to the blower wheel. The snow is transported upwardly in the snow-clearing worm gears and is thrown in front of the blower wheel openings. This effect can be achieved as long as the snow is loose. If the snow is wet and heavy, snow easily jams in front of the blower wheel. In that case the snow-clearing worm gears turn idly, and the blower wheel pushes a wall of snow before it, without having the snow reach the interior of the machine. A precutting device which rotates between the worm gears is largely ineffective since its diameter is limited to the spacing between the worm gears and since it does not operate close to the ground.
By contrast with the prior art, the invention is based on the objective of improving a snowblower of the type mentioned above so that it is also effective with wet, heavy snow.
According to the invention, this is achieved by providing the precutting device with radial arms, each having a radius corresponding approximately to that of the blower wheel. The rotating bodies that are formed by the precutting device, and by the snow-clearing worm gears, are phased with respect to one another as seen from the top of the machine. The result is that the respective rotating parts interact without contact.
The invention not only provides a non-contacting engagement of the cutting arms of the precutting device, and of the snow-clearing worm gears, it also provides that the snow-clearing worm gears are appropriately proportioned so that the rotating bodies are near to one another without making actual contact. It is desirable for the snow-clearing worm gears at an appropriate low level, so that the precutting device extends above them. The snow-clearing worm gears preferably have deflecting plates on their backsides, where these plates pivot about vertical axes. Consequently the snow which is grasped and transported upwardly can not be blown laterally or backwards.
As with known snowblowers, the snow-clearing worm gears can be disposed so that they can pivot about vertical axes. Thus the spacing between them is variable. In this connection, the invention provides that the minimum spacing between the vertical axes of the snow-clearing worm gears is slightly larger than the diameter of the blower wheel. With this arrangement, the snow-clearing worm gears remain effective for feeding snow into the opening of the blower wheel. Because of the mutual engagement of the worm gears and the precutting device, it is possible that the cutting arms can be suitably long, approximately equal to the diameter of the cutting wheel. Thus even if layers of snow close to the ground are loosened by the precutting device the buildup of snow blockage, especially with very moist snow is avoided both in front of the wheel and in front of the snow-clearing worm gears. The dimentioning of the precutting device also facilitates better cutting of frozen snow.
In a preferred embodiment, the snow-clearing worm gears have a height which corresponds approximately to the diameter of the blower wheel. Their center section is designed to fit in accordance with the diameter of the precutting device. With this embodiment the snowblower can clear relatively high walls of snow and snow drifts.
In another embodiment, the snow-clearing worm gears extend from the vicinity of ground level to a horizontal plan through the rotational axis of the blower wheel. Their upper section is matched to the rotational form of the precutting device. This embodiment can be produced economically since the snow-clearing worm gears can be relatively short. In addition, this embodiment is adequate for most snow clearing purposes, at least for snow with a height lying below the rotational axis of the blower wheel.
In keeping with the invention, the precutting device can be of arbitrary design. The cutting arms can be straight or spiral in shape. They can have cutting surfaces or they can spread in a circumferential direction along their ends. They also can be composed of radial cutting bars and throw bars that run in a circumferential direction.